NACE SP0214

Abstract

Introduction <br>The water-usage systems addressed in this standard are as follows. (Note: this list covers all piping systems in residential and office buildings; it is not applicable to industrial facilities.) <br>GROUP I: The predominant water-usage systems in most buildings consisting of potable water (hot and cold); steam and condensate systems; and waters for heating, ventilation, and air conditioning (HVAC) (open and closed systems) <br>GROUP II: Waste water&#226;&#8364;&#8221;sewage and drainage <br>GROUP III: Higher quality waters&#226;&#8364;&#8221;preconditioning systems and boilers <br>GROUP IV: Fire-protection systems&#226;&#8364;&#8221;wet, dry, foam, and other systems <br>GROUP V: Architectural systems&#226;&#8364;&#8221;fountains, waterfalls, and other displays <br>Group I: Highest Water-Usage Systems in Buildings The Group I piping systems include the potable-water system and building systems that are major users of potable water.&#160; <br>Potable-water systems are seldom cleaned except when flow conditions or leakage mandate that maintenance be performed. The U.S. Environmental Protection Agency (EPA)⁽¹⁾ requires these systems to be sanitized before being placed back into operation to prevent transmission of disease.¹&#160; <br>Steam systems typically use high-purity water, which ensures long life of the generating equipment or the steam piping systems. The condensate system, however, requires treatment to make it less susceptible to corrosion. This piping system usually requires more attention than the steam system.&#160; <br>HVAC systems may be open or closed, depending on the design of the system. Open-condenser water systems usually have a cooling tower and associated highwater usage. Water treatment programs are critical for open and closed HVAC systems.&#160; <br>Closed systems require little to no make-up water because there is no draining or blow-down. Replacement water is added only when the system is opened or drained for maintenance, or because of unavoidable leakage from components or piping connectors. Closed heating/cooling systems may require cleaning because of interior fouling. <br>Group II: Waste waters and Drain Waters&#160; <br>Wastewater and drain-water systems are almost never chemically treated (except for grease disposal) and are discharged from the building into the local sewage system for processing. This may be the building's own leaching field, a local sewer system and water treatment facility, or a major metropolitan wastewater treatment program. It is common practice for hotels and restaurants to chemically treat grease traps and ejector pits.&#160; <br>Wastewater and drain water piping systems are rarely cleaned except when the system is inoperative. The cleaning is primarily mechanical, such as high-pressure water washing or mechanical rotor cleaning, if such cleaning is appropriate.&#160; <br>Group III: Systems Requiring High-Quality Waters <br>Higher-quality water is required for the operation of some equipment, such as boiler feed water systems. Additional equipment, such as reverse-osmosis (RO) systems or sodium zeolite systems, may be required to condition the water.&#160; <br>Group IV: Fire-Suppression Water Systems <br>Wet systems are filled and allowed to remain stagnant without circulation and usually without treatment. Recent sprinkler code changes require that where microbiologically influenced corrosion (MIC) concerns are suspected, water treatment chemicals shall be used.&#160; <br>Wet systems are connected to, but isolated from, the main potable water system by means of a backflow prevention device.&#160; <br>Generally, there is no active circulation in the stand pipes, except during testing periods; there may be limited circulating, charged headers in certain systems. Dry systems are pressurized with air or nitrogen. <br>These systems may be damp because of periodic hydrostatic testing or internal condensation if used outside, where a risk of freezing exists. This interior moisture condition can lead to severe unexpected corrosion problems with leakage occurring from the inside of the pipe.&#160; <br>Group V: Architectural Applications&#226;&#8364;&#8221;Fountains, Waterfalls, Display Uses These systems are usually open recirculating systems with wide open basins, full-stream filters, and circulating pumps. Piping is mostly polyvinyl chloride (PVC), although copper and steel pipes are sometimes used. System water is usually accessible to the public for decorative display. It is kept clean with full-stream filtration and intermittent treatment with oxidizing biocide for esthetic purposes. Open areas are mechanically cleaned on a regular basis.&#160; <br>Cleaning can only provide clean surfaces, which represent original piping minus the corrosion loss. Lost wall thickness and pipe wall damage from pitting corrosion cannot be restored.&#160; <br>However, cleaning provides the option of restarting with a deposit-free, clean system that responds to properly treated water by minimizing the corrosion rate. Cleaning has the added benefit of maximizing the life of the remaining pipe. <br>⁽¹⁾ Environmental Protection Agency (EPA), Ariel Rios Building, 1200 Pennsylvania Ave. N.W., Washington, DC 20460.